1. Field of the Invention
The invention concerns a compact smart card reader.
2. Description of the Prior Art
A smart card reader is usually a subsystem within a system such as a sales transaction terminal, a taxiphone, etc. It is used to read or write information in a silicon integrated circuit microchip. The chip is accommodated within the thickness of a card and is accessible electrically via conductive lands on the card surface. A reader usually comprises: a connector, a printed circuit board carrying electronic components and the connector, a case which is generally shared by the reader and other subsystems of a system, and means for fixing the printed circuit board to the case.
The card is inserted into the connector through a slot in the case. The connector conventionally comprises means for guiding the card as it is inserted into the connector, means for positioning it accurately within the connector and spring contacts bearing on the conductive lands on the card to make the connections. Accurate positioning of the card relative to the spring contacts is vital to obtaining a low contact resistance without rapid wear of the conductive lands and the spring contacts.
It is known, specifically from French patent application No 2 623 313, to produce a smart card connector comprising a plastics material frame carrying the spring contacts and a cover parallel to the plane of the frame and to the plane of the card. This document describes a card connector in which all dimensional tolerances are determined by the contact-holder frame, which can be a molded part combining great accuracy with low cost. Movement of the card in its own plane is guided by two parallel slideways which are integrated into the cover or into the frame. The cover rests on supports integral with the frame and defining accurately the gap between the cover and the frame. The cover determines the distance between the card and the spring contacts. It applies pressure to the card as a reaction force to the pressure exerted by the contacts.
A number of centering studs are integrated into the frame and nested within holes on the cover position the cover relative to the frame. The cover is riveted or screwed to the frame. The connector assembly is conventionally fixed to a printed circuit board by soldering leads which extend the spring contacts. The printed circuit board may be screwed or riveted to a case.
European patent application EP 0 274 288 describes a smart card reader adapted to be mounted inside an electronic system and comprising:
a case in two parts surrounding the reader assembly; PA0 a printed circuit board carrying on one side the electronic components of the reader; PA0 a smart card connector primarily comprising an insulative frame carrying spring contacts. PA0 a case enclosing the other parts of the reader; PA0 a printed circuit board; PA0 means for fixing the printed circuit board to the case: and PA0 a smart card connector comprising:
The insulative frame is overmolded onto the spring contacts. The frame is disposed on the same side as the printed circuit board as the components. One end of each spring contact passes through the printed circuit board and is soldered to the unoccupied side of the board. The printed circuit board and the frame are enclosed between the two parts of the case. The frame is positioned relative to the first part, on the unoccupied side of the printed circuit board, by two pegs which pass with clearance through two holes in the printed circuit board and nest within two holes in the first part. The second part, on the side carrying the frame and the components, is fixed to the first part at its perimeter.
The second part serves as a guide table for the smart card and exerts on it a pressure as a reaction force to the pressure of the spring contacts. It therefore has the same function as the cover of the connector described in French patent application No 2 623 313. The device described in European patent application No 0 274 288 is therefore simpler than that described in French patent application No 2 623 313, but is wanting in precision. The position of the card relative to the spring contacts depends on the assembly tolerances of the frame relative to the first case part plus the assembly tolerances of the first case part relative to the second part, which guides the card.
Consideration is being given to producing portable devices incorporating a smart card reader. For example, pocket radiotelephones may incorporate a smart card reader as a means of payment, as a means of identifying the user, etc. For applications like these it is desirable to minimize the overall dimensions of the smart card reader and possibly also to reduce its cost to encourage adoption of this type of device by the public.
An object of the invention is to reduce the overall dimensions of a device of this kind without compromising the accuracy with which the card is positioned relative to the contacts.